Background Vessels made of plastic are used for many purposes such as storing liquids, dispersions, powder or granulates. There is often a requirement to connect various types of arrangement to the vessel. Examples of such arrangements are hoses, pipes and pumps for conveying the contents to or from other units. Other examples are heating devices, and devices for measuring, for example, temperature, pressure or level. Mounting these arrangements, or connection devices for them, does not present any great problems as long as the vessel is open so that both the inside and the outside are accessible. In most cases, fastening is then carried out by nuts from the rear side of the arrangement.

When the vessels are tanks, often with only a small filling hole, it is difficult, however, to use tools from the inside, and the necessity of mounting exclusively from the outside is evident. The description below relates to vessels of this type, that is to say tanks of various types made essentially from a thermoplastic material. Examples of areas of application of such tanks are coolant tanks for workshop machines for cutting machining, electric arc cutting or welding. Examples from the area of office machinery are containers for lubricants, toner or developer in copying machines. Within the automotive

industry, containers for windscreen washing liquid or expansion tanks for the cooling system are examples.

In thick-walled vessels, it is possible to tap directly into the vessel wall, which affords a possibility for mounting from the outside. A disadvantage of this method is that, in addition to making a hole in the vessel, it also requires a tapping operation before mounting. Moreover, as the wall thickness decreases, it becomes increasingly difficult to maintain leaktightness permanently in such a joint, especially if the joint is subjected to varying lateral forces or great temperature changes.

Vessels of the type in question are in most cases made by blow-moulding and sometimes by rotational moulding. It is then possible to integrate into the mould inlet and outlet connections for the tank in the form of hose connection pieces. This procedure is very common. The disadvantage of the method is that it requires time-consuming burr-removal work after production of the tank if sufficiently smooth surfaces for leaktight hose connections are to be achieved. The reason for this is that it is difficult, in such a large mould as one for a tank, to obtain sufficiently close tolerances for the considerably smaller connection piece. Moreover, this method is limited to hose connection at predetermined locations on the vessel. Mounting of sensors and various members performing functions, such as pumps and heating units, can seldom be carried out using this method. Problems likewise arise in the case of tanks in which an alternative configuration is applied, especially if there are requirements for different hole diameters.

Another variant of mounting from the outside involves an elastic packing, which has a flange which rests on the outside of the vessel wall, being positioned in the hole before the arrangement concerned is pressed in. Owing to the fact that the bottom part of the arrangement is wider than the rest of the material passing through the hole, and this part lies

behind the elastic packing after mounting, the packing will be pressed together when an attempt is made to pull out such an arrangement. The demounting force necessary is thus greater than the mounting force. Nevertheless, it is difficult to make such a joint permanently leaktight, especially if the joint is subjected to varying lateral forces and temperature. In addition, there is often a need for some form of friction-reducing lubrication for the mounting. This also reduces the resistance to being pulled out. A further problem is ageing of the elastic material.

Sometimes, this problem is exacerbated by the contents of the tank being aggressive.

Object of the invention The object of the invention is to indicate an arrangement which provides a solution to the abovementioned problems without having the disadvantages inherent in the known art.

According to the invention, this object is achieved by an arrangement which comprises on the one hand a first surface designed in such a manner that, during mounting, this surface, when pressed and/or rotated relative to the plastic vessel, pushes aside the vessel wall around a mounting hole located in the vessel, and on the other hand a second surface adapted so as, after mounting, to establish sealing contact against the inside of the vessel wall, which has sprung back, and also a securing device which is adapted so as, from the outside of the vessel, to fix the arrangement in relation to the vessel and bring about pressure between the vessel wall and said second, sealing surface.

Members performing functions may be, for example, a pump or a heating unit, and measuring members may be, for example, temperature, pressure or level sensors. Thin-walled plastic vessels are primarily vessels made of a thermoplastic material

having a material thickness at the mounting location of 0.5-4.0 mm, preferably 1-3 mm.

Also indicated is a tool for mounting such arrangements according to the above, which have an essentially centrally positioned axial through-hole and are referred to as nipples below, for connecting pipes or hoses. The tool comprises a rod adapted to the dimension of the hole of the nipple and a plane surface for transmitting force to the nipple as the latter is mounted in the vessel wall.

Mounting is effected by the nipple, with the associated securing device, being positioned on the rod and, by means of a distinct pressure, being made to snap into the hole in the vessel wall. The nipple is then fixed by the nut being tightened from the outside.

A washer between the vessel wall and the nut distributes the force and contributes to establishing a leaktight joint. A cup spring can be used in order to ensure permanent pressure in the joint. Instead of a nut, an axially acting locking washer can be used in the securing device. This usually allows more rapid mounting than in the case of a nut.

Additional embodiments of the tool are indicated. A second embodiment includes a separate hollow body for positioning in front of the nipple during mounting. This hollow body has an outer surface which constitutes an extension of the nipple. This is a cost-effective method if the cost of the nipple material is high, and savings can thus be made by shortening the nipple. The hollow body is shaken out of the vessel through the filling hole after nipple mounting and reused. Alternatively, if this is not possible, a less expensive material can be used for the hollow body, and this can be left in the vessel after mounting.

A third embodiment of the tool integrates the making of a hole in the vessel wall into the mounting operation. The hollow body mentioned previously is then provided with a cutting edge and mounting is then

effected by combined rotation and pressing of the tool against the vessel wall. In this embodiment, it is advantageous if the end of the rod of the tool is pointed and the length of the rod is such that, during mounting, only so much of the point protrudes in front of the hollow body that a secure grip in a centring hole in the vessel wall can be maintained during cutting out of the mounting hole for the nipple.

Also indicated is a plastic vessel with an arrangement according to the description above mounted thereon.

Brief description of the drawings Fig. 1 shows a hose connection for mounting from the outside of a vessel, according to the prior art, with a packing made of elastic material.

Fig. 2 shows an arrangement for hose connection according to the present invention. Fig. 2a shows an embodiment in which a hollow cone belonging to the mounting tool forms an extension of the arrangement itself. Figs 2c-2d are the arrangement according to 2a or 2b seen from above and Figs 2e-2f the same seen from below.

Fig. 3 shows an embodiment of the tool with a separate hollow cone and a connection arrangement, in the form of a hose nipple, at various stages during mounting in the vessel wall.

Fig. 4 shows the tool according to the invention in an embodiment for making a hole in the vessel wall in conjunction with mounting of the connection device.

Fig. 5 shows some different embodiments of the connection arrangement according to the invention.

Fig. 6 shows on enlarged scale three different embodiments of a sealing surface for the arrangement according to the invention.

Fig. 7 indicates some further examples of application of the invention. Fig. 7a is a sensor with

a flat-pin connection, 7b a heating unit, 7c a hose connection with a pipe extension and, finally, 7d an electric pump unit.

Description of preferred embodiments The invention is now described in the form of examples with reference to the appended drawings.

The prior art most near at hand illustrated in Fig. 1 serves as the starting point. Fig. la is a hose connection nipple and Fig. 1b a rubber packing. This packing is positioned in the pre-made hole in the vessel, after which the nipple is pressed in. As can be seen from Fig. lc, the rubber packing is pressed out on the inside of the vessel wall by the wider lower edge of the nipple. If an attempt is made to pull the nipple out after mounting, the packing is pressed together even more. This makes demounting more difficult. However, sealing is effected only along the hole edge and therefore depends to a great extent on the tolerances of the hole diameter and ovality and also the condition of the packing. As no separate fixing of the nipple is effected, it can be inclined under lateral loading, increasing the risk of leakage. Both nipple and packing must be made specifically for the application concerned. This becomes costly for small and medium-sized volumes.

The invention eliminates the problems with the immediate prior art in a radical manner. Only one specially produced component is required, that is to say the nipple. The securing device consists of standard components such as a nut, a washer, a cup spring, and a locking washer. This leads to clear advantages in terms of cost. Sealing is effected against a larger surface area along the inside of the vessel wall instead of only along the hole wall. This means that the leaktightness does not depend on the abovementioned tolerances. No ageing rubber material is present. Fixing by means of a nut or locking washer

means that the nipple is on the whole insusceptible to lateral forces.

Figs 2a, 2f and 6a show the best embodiment of the hose connection if the nipple is made of expensive material such as stainless steel or brass. The front part of the nipple is then made in the form of a greatly truncated cylindrical cone, the bounding surface 10 of which serves to widen the hole in the vessel wall at the moment of mounting. The hollow body 30, the bounding surface of which constitutes a direct extension of the surface 10, is a part of the mounting tool which also consists of a rod 50; 150, a surface 45; 145, essentially at right angles to the rod, and, in the case of manual mounting, a handle 40. The hollow body makes possible sufficient widening of the hole in the vessel wall in order to snap the nipple in so that its sealing surface 20 comes to lie inside the vessel.

This sealing surface is designed so that the periphery forms an edge directed towards the inside of the vessel wall. This edge penetrates the vessel wall when the securing device, consisting of a nut 15 and a cup spring 16, is tightened. In this way, a joint with permanent leaktightness is established.

If, on the other hand, the nipple is made of a less expensive material, for example a plastic material, the embodiment according to Figs 2b, 2f and 6a is preferred. No separate hollow body 30 for the tool is used in this case but the bounding surface 110 is itself then sufficiently extensive to widen the mounting hole.

According to the patent claims, the first surface 10; 110; 210; 310, which is to push aside the vessel wall at the moment of mounting, can be designed in very different ways. 35 in Fig. 2e indicates an octagonal cone instead of a circular one. The figures are only examples. The only requirement is that this surface will facilitate the pushing aside of the vessel wall at the moment of mounting. The fact that the generated line according to Patent Claim 2 can be

represented mathematically by a continuous and essentially monotonic function and that this line is moved along a curve 35; 135 is, however, a reasonable requirement, and all the examples in the figures fulfil this.

With regard to the securing device, it may be advantageous to include, in addition to the nut 115 and the cup spring 116, a plane washer 117 to distribute the force against the wall 55. An axially acting locking washer 215 in place of the nut 15; 115 simplifies mounting. When the nut is tightened, it is an advantage if there is some form of wrench grip, for example at the front edge of the hose connection 25.

Another method of embodiment is that the hole in the nipple has an internal hexagonal shape as in Fig. 2c, and that the tool rod in the same embodiment 150 corresponds to this.

A second sealing surface 20; 120; 220 consists of a plane surface. Some form of edge or raised portion directed towards the vessel wall improves the sealing further because it penetrates the vessel wall. The design according to 20 is to be preferred because it provides secure and permanent sealing at the same time as being easy to produce.

The mounting sequence is shown in Figure 3.

Clearly, aids in the form of a lever, of the drill support type, or equipment which is automated to a greater or lesser degree can also be used. The handle 40 of the tool is then replaced with a machine adapter.

It is also possible to integrate the making of a hole into the mounting sequence. The tool is then designed according to Fig. 4. The rod is provided with an end point 160 for centring the tool. The hollow body 130 is provided with a cutting edge 165 and the rod 150 and the hole in the hollow body are designed so that the hollow body co-rotates when the tool is rotated, for example by means of an internal hexagonal shape as shown in the figure. The overall length of the rod will

in this case be slightly greater than the sum of the lengths of the nipple and the hollow body.

Application of the invention goes far beyond a hose connection for thin-walled plastic vessels.

Clearly, instead of the hose connection design 25, this part can be designed for connection of pipes by, for example, screw threads. As mentioned previously, other examples of applications are given in Figure 7, where the active first surface 10; 110; 210; 310 and the second, sealing surface 20; 120; 220 can be integrated into different types of members performing functions or carrying out measurements.